diff options
Diffstat (limited to 'libavdevice/timefilter.c')
| -rw-r--r-- | libavdevice/timefilter.c | 46 |
1 files changed, 32 insertions, 14 deletions
diff --git a/libavdevice/timefilter.c b/libavdevice/timefilter.c index 8b98d338f0..ba2e54e0c0 100644 --- a/libavdevice/timefilter.c +++ b/libavdevice/timefilter.c @@ -5,20 +5,20 @@ * Author: Olivier Guilyardi <olivier samalyse com> * Michael Niedermayer <michaelni gmx at> * - * This file is part of Libav. + * This file is part of FFmpeg. * - * Libav is free software; you can redistribute it and/or + * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * - * Libav is distributed in the hope that it will be useful, + * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public - * License along with Libav; if not, write to the Free Software + * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ @@ -37,14 +37,21 @@ struct TimeFilter { int count; }; -TimeFilter *ff_timefilter_new(double clock_period, - double feedback2_factor, - double feedback3_factor) +/* 1 - exp(-x) using a 3-order power series */ +static double qexpneg(double x) +{ + return 1 - 1 / (1 + x * (1 + x / 2 * (1 + x / 3))); +} + +TimeFilter *ff_timefilter_new(double time_base, + double period, + double bandwidth) { TimeFilter *self = av_mallocz(sizeof(TimeFilter)); - self->clock_period = clock_period; - self->feedback2_factor = feedback2_factor; - self->feedback3_factor = feedback3_factor; + double o = 2 * M_PI * bandwidth * period * time_base; + self->clock_period = time_base; + self->feedback2_factor = qexpneg(M_SQRT2 * o); + self->feedback3_factor = qexpneg(o * o) / period; return self; } @@ -69,11 +76,16 @@ double ff_timefilter_update(TimeFilter *self, double system_time, double period) loop_error = system_time - self->cycle_time; self->cycle_time += FFMAX(self->feedback2_factor, 1.0 / self->count) * loop_error; - self->clock_period += self->feedback3_factor * loop_error / period; + self->clock_period += self->feedback3_factor * loop_error; } return self->cycle_time; } +double ff_timefilter_eval(TimeFilter *self, double delta) +{ + return self->cycle_time + self->clock_period * delta; +} + #ifdef TEST #include "libavutil/lfg.h" #define LFG_MAX ((1LL << 32) - 1) @@ -85,17 +97,21 @@ int main(void) #define SAMPLES 1000 double ideal[SAMPLES]; double samples[SAMPLES]; + double samplet[SAMPLES]; for (n0 = 0; n0 < 40; n0 = 2 * n0 + 1) { for (n1 = 0; n1 < 10; n1 = 2 * n1 + 1) { double best_error = 1000000000; double bestpar0 = 1; - double bestpar1 = 0.001; + double bestpar1 = 1; int better, i; av_lfg_init(&prng, 123); for (i = 0; i < SAMPLES; i++) { - ideal[i] = 10 + i + n1 * i / (1000); + samplet[i] = 10 + i + (av_lfg_get(&prng) < LFG_MAX/2 ? 0 : 0.999); + ideal[i] = samplet[i] + n1 * i / (1000); samples[i] = ideal[i] + n0 * (av_lfg_get(&prng) - LFG_MAX / 2) / (LFG_MAX * 10LL); + if(i && samples[i]<samples[i-1]) + samples[i]=samples[i-1]+0.001; } do { @@ -107,7 +123,9 @@ int main(void) TimeFilter *tf = ff_timefilter_new(1, par0, par1); for (i = 0; i < SAMPLES; i++) { double filtered; - filtered = ff_timefilter_update(tf, samples[i], 1); + filtered = ff_timefilter_update(tf, samples[i], i ? (samplet[i] - samplet[i-1]) : 1); + if(filtered < 0 || filtered > 1000000000) + printf("filter is unstable\n"); error += (filtered - ideal[i]) * (filtered - ideal[i]); } ff_timefilter_destroy(tf); |